Broadcasting management information using fountain codes

ABSTRACT

Technologies for broadcasting management information include a management server and a number of client devices. The management server encodes management data such as a certificate revocation list into a number of message fragments using a fountain code encoding algorithm and broadcasts the message fragments continually over a network. Each client device analyzes the network during a boot process to receive the broadcast message fragments. Each client device decodes the message fragments using a fountain code decoding algorithm and determines whether the message is complete. If the message is complete, the client device parses the message to retrieve the management data and may install the management data on the client device. If the message is incomplete, the client device may store the message fragments in nonvolatile storage for processing during future boot events. The client device may perform those operations in a pre-boot firmware environment. Other embodiments are described and claimed.

BACKGROUND

Enterprises and other organizations may manage large installations ofnetwork-attached machines such as computers, mobile devices, servers,and network infrastructure. The number of managed network-attacheddevices is likely to continue to increase as networking capabilities areadded to more classes of devices, up to and including large numbers ofubiquitous embedded devices. Often, identical management informationmust be provided to large classes of managed devices. For example, thesame security certificate revocation information may be provided toevery secure-boot-enabled machine managed by an enterprise. Typicalapproaches for installing management information include multicastingmanagement information to a large class of homogeneous machines inparallel. However, such approaches typically require synchronizationbetween the sender and receivers, meaning that a large number ofreceiving devices may be required to synchronize their activity (forexample, by listening for multicast information at the same time).Another typical approach for installing management information includesdownloading management information from a server by an operating systemcomponent or user-mode software application in response to a userrequest or as a scheduled download. However, such approaches may requireuser intervention and may be vulnerable to malware and/or securityexploits of the operating system and/or software application.

Rateless erasure codes, also known as fountain codes, encode a finiteset of k input symbols into an unbounded set of encoded symbols. Theinput symbols may be decoded from any k′ encoded symbols, where k′ maybe equal to k or slightly larger than k. Common fountain codes includeLuby transform codes (LT codes) and Raptor codes. Typical uses forfountain codes include encoding video signals for delivery over aninternet protocol (IP) network.

BRIEF DESCRIPTION OF THE DRAWINGS

The concepts described herein are illustrated by way of example and notby way of limitation in the accompanying figures. For simplicity andclarity of illustration, elements illustrated in the figures are notnecessarily drawn to scale. Where considered appropriate, referencelabels have been repeated among the figures to indicate corresponding oranalogous elements.

FIG. 1 is a simplified block diagram of at least one embodiment of asystem for broadcasting management information from a management serverto a number of client devices;

FIG. 2 is a simplified block diagram of at least one embodiment ofvarious environments that may be established by the system of FIG. 1;

FIG. 3 is a simplified flow diagram of at least one embodiment of amethod for broadcasting management information that may be executed bythe management server of FIGS. 1 and 2;

FIG. 4 is a simplified schematic diagram of at least one embodiment of aboot process that may be executed by a client device of FIGS. 1 and 2;and

FIG. 5 is a simplified flow diagram of at least one embodiment of amethod for receiving broadcast management information that may beexecuted by a client device of FIGS. 1 and 2.

DETAILED DESCRIPTION OF THE DRAWINGS

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific embodiments thereof havebeen shown by way of example in the drawings and will be describedherein in detail. It should be understood, however, that there is nointent to limit the concepts of the present disclosure to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives consistent with the presentdisclosure and the appended claims.

References in the specification to “one embodiment,” “an embodiment,”“an illustrative embodiment,” etc., indicate that the embodimentdescribed may include a particular feature, structure, orcharacteristic, but every embodiment may or may not necessarily includethat particular feature, structure, or characteristic. Moreover, suchphrases are not necessarily referring to the same embodiment. Further,when a particular feature, structure, or characteristic is described inconnection with an embodiment, it is submitted that it is within theknowledge of one skilled in the art to effect such feature, structure,or characteristic in connection with other embodiments whether or notexplicitly described. Additionally, it should be appreciated that itemsincluded in a list in the form of “at least one A, B, and C” can mean(A); (B); (C): (A and B); (B and C); or (A, B, and C). Similarly, itemslisted in the form of “at least one of A, B, or C” can mean (A); (B);(C): (A and B); (B and C); or (A, B, and C).

The disclosed embodiments may be implemented, in some cases, inhardware, firmware, software, or any combination thereof. The disclosedembodiments may also be implemented as instructions carried by or storedon a transitory or non-transitory machine-readable (e.g.,computer-readable) storage medium, which may be read and executed by oneor more processors. A machine-readable storage medium may be embodied asany storage device, mechanism, or other physical structure for storingor transmitting information in a form readable by a machine (e.g., avolatile or non-volatile memory, a media disc, or other media device).

In the drawings, some structural or method features may be shown inspecific arrangements and/or orderings. However, it should beappreciated that such specific arrangements and/or orderings may not berequired. Rather, in some embodiments, such features may be arranged ina different manner and/or order than shown in the illustrative figures.Additionally, the inclusion of a structural or method feature in aparticular figure is not meant to imply that such feature is required inall embodiments and, in some embodiments, may not be included or may becombined with other features.

Referring now to FIG. 1, in the illustrative embodiment, a system 100for broadcasting management data includes a management server 102 and anumber of client devices 104 capable of communication over a network106. In use, as described below, the management server 102 continually,periodically, or responsively broadcasts updated management data overthe network 106 that has been encoded with a rateless erasure code, alsoknown as a “fountain code.” Whenever a client device 104 is booted, theclient device 104 analyzes the network 106 to receive message fragmentsbroadcast by the management server 102. After a sufficient number ofmessage fragments have been received, the client device 104 decodes themessage fragments (applying an algorithm appropriate to the particularfountain code in use) and recovers the management data for installation.The client device 104 may collect message fragments over more than oneboot cycle before being able to decode a complete message. The disclosedtechnologies allow standardized management information to be broadcastby a single management server 102 to a large number of client devices104 asynchronously. In other words, the client devices 104 are notrequired to synchronize their boot events and may sample the network 106at arbitrary times, for arbitrary durations. Thus, the client devices104 may be managed with improved performance and/or scalability.Additionally, the management data may be received and installed byfirmware on the client device 104 without the involvement of anyoperating system of the client device 104. Therefore, potentialexploits, vulnerabilities, or software defects in the operating systemmay be avoided, improving management security and/or reliability.

The management server 102 may be embodied as any type of device forbroadcasting management information as described herein. For example,the management server 102 may be embodied as, without limitation, aserver computer, a workstation, a desktop computer, a smart phone, atablet computer, a laptop computer, a notebook computer, a mobilecomputing device, a cellular telephone, a handset, a messaging device, avehicle telematics device, a distributed computing system, amultiprocessor system, a consumer electronic device, and/or any othercomputing device configured to perform the functions described herein.Further, the management server 102 may be embodied as a single servercomputing device or a collection of servers and associated devices. Forexample, in some embodiments, the management server 102 is embodied as acloud service to perform the functions described herein. In suchembodiments, the management server 102 may be embodied as a “virtualserver” formed from multiple computing devices distributed across thenetwork 106 and operating in a public or private cloud. Accordingly,although the management server 102 is illustrated in FIG. 1 anddescribed below as embodied as single server computing device, it shouldbe appreciated that the management server 102 may be embodied asmultiple devices cooperating together to facilitate the functionalitydescribed below.

As shown in FIG. 1, the illustrative management server 102 includes aprocessor 120, an input/output subsystem 122, a memory 124, and a datastorage device 126. Of course, the management server 102 may includeother or additional components, such as those commonly found in a serverand/or a stationary computer (e.g., various input/output devices), inother embodiments. Additionally, in some embodiments, one or more of theillustrative components may be incorporated in, or otherwise form aportion of, another component. For example, the memory 124, or portionsthereof, may be incorporated in the processor 120 in some embodiments.

The processor 120 may be embodied as any type of processor capable ofperforming the functions described herein. For example, the processor120 may be embodied as a single or multi-core processor(s), digitalsignal processor, microcontroller, or other processor orprocessing/controlling circuit. Similarly, the memory 124 may beembodied as any type of volatile or non-volatile memory or data storagecapable of performing the functions described herein. In operation, thememory 124 may store various data and software used during operation ofthe management server 102 such as operating systems, applications,programs, libraries, and drivers. The memory 124 is communicativelycoupled to the processor 120 via the I/O subsystem 122, which may beembodied as circuitry and/or components to facilitate input/outputoperations with the processor 120, the memory 124, and other componentsof the management server 102. For example, the I/O subsystem 122 may beembodied as, or otherwise include, memory controller hubs, input/outputcontrol hubs, firmware devices, communication links (i.e.,point-to-point links, bus links, wires, cables, light guides, printedcircuit board traces, etc.) and/or other components and subsystems tofacilitate the input/output operations. In some embodiments, the I/Osubsystem 122 may form a portion of a system-on-a-chip (SoC) and beincorporated, along with the processor 120, the memory 124, and othercomponents of the management server 102, on a single integrated circuitchip.

The data storage device 126 may be embodied as any type of device ordevices configured for short-term or long-term storage of data such as,for example, memory devices and circuits, memory cards, hard diskdrives, solid-state drives, or other data storage devices. The datastorage device 126 may store management data to be broadcast to theclient devices 104.

The management server 102 further includes a communication circuit 128,which may be embodied as any communication circuit, device, orcollection thereof, capable of enabling communications between themanagement server 102, the client devices 104, and/or other remotedevices. The communication circuit 128 may be configured to use any oneor more communication technology (e.g., wireless or wiredcommunications) and associated protocols (e.g., Ethernet, Bluetooth®,Wi-Fi®, WiMAX, etc.) to effect such communication. The communicationcircuit 128 may be embodied as a network adapter, including a wirelessnetwork adapter.

Each client device 104 may be embodied as any type of device forperforming the functions described herein. For example, each clientdevice 104 may be embodied as, without limitation, a smart phone, atablet computer, a laptop computer, a notebook computer, a mobilecomputing device, a wearable computing device, a cellular telephone, ahandset, a messaging device, a vehicle telematics device, a servercomputer, a workstation, a distributed computing system, amultiprocessor system, a consumer electronic device, and/or any othercomputing device configured to perform the functions described herein.As such, each client device 104 may include components and featuressimilar to the management server 102, such as a processor 140, I/Osubsystem 142, memory 144, data storage 146, communication circuitry148, and various peripheral devices. Those individual components of eachclient device 104 may be similar to the corresponding components of themanagement server 102, the description of which is applicable to thecorresponding components of each client device 104 and is not repeatedfor clarity of the present description.

Each client device 104 further includes a firmware cache 150. Thefirmware cache 150 may be embodied as any device that is accessible to afirmware environment of the client device 104 and is configured forpersistent storage of data while the client device 104 is powered downor disconnected from a power supply. In the illustrative embodiment, thefirmware cache 150 is embodied as a platform flash memory chip. In otherembodiments, the firmware cache 150 may be embodied as an embeddednon-volatile memory system (e.g., an eMMC device) or as part of afirmware volume maintained on a system partition of the data storagedevice 146. Thus, in some embodiments, the firmware cache 150 may beincorporated into one or more other components of the client device 104,for example into the I/O subsystem 142. As described below, the firmwarecache 150 may be used to persistently store broadcast message fragmentsreceived by the client device 104.

In some embodiments, one or more of the client devices 104 may alsoinclude a manageability engine 152. The manageability engine 152 isembodied as a device that provides remote configuration, control, ormanagement of the client device 104. The illustrative manageabilityengine 152 includes an out-of-band processor 154. The out-of-bandprocessor 154 is separate and distinct from the main processor 140 ofthe client device 104. As such, the manageability engine 152 is capableof operating independently of the state of the rest of the client device104. That is, the manageability engine 152 is capable of operatingregardless of the operating state of the processor 140, including whenthe client device 104 is powered off, when the client device 104 isexecuting a pre-boot firmware environment, when an operating system ofthe client device 104 is active, and when the operating system iscrashed or otherwise inactive. The manageability engine 152 is alsocapable of communicating using the communication circuit 148independently of the state of the client device 104, also known as“out-of-band” communication. In some embodiments, the manageabilityengine 152 may include a dedicated network adaptor for such out-of-bandcommunication, in addition to, or instead of, connecting via thecommunication circuit 148. In some embodiments, the manageability engine152 may be incorporated into or otherwise form a part of the I/Osubsystem 142. Thus, in some embodiments the manageability engine 152may analyze the network 106 to receive message fragments broadcast bythe management server 102 and either installed recovered management datadirectly or alternately expose the recovered management data forinstallation by the platform firmware upon a restart event.

Referring now to FIG. 2, in some embodiments the management server 102establishes an environment 200 during operation. The illustrativeenvironment 200 includes a client management module 202, a fountainencoding module 204, and a broadcast module 206. The various modules ofthe environment 200 may be embodied as hardware, firmware, software, ora combination thereof.

The client management module 202 is configured to receive or retrievemanagement data that is to be broadcast to one or more of the clientdevices 104. The management data may include any information, code,settings, or other data that may be used to provision, configure, orotherwise manage the client devices 104. For example, the managementdata may include certification revocation lists or other data used toimplement an enterprise security policy, firmware images, or softwareapplications. In the illustrative embodiment, the management data isincluded in the management database 208 referenced by the clientmanagement module 202. The management data may be provided or maintainedby a network administrator, an enterprise server, or any other sourceresponsible for managing the client devices 104.

The fountain encoding module 204 is configured to encode the managementdata into a stream of message fragments using a fountain code. Asdescribed further below, fountain codes, also known as rateless erasurecodes, allow a finite source message to be encoded into a practicallyunlimited number of encoded output symbols or message fragments.Receivers of the encoded data may recover the source message from anymessage fragments received, as long as more than a threshold number ofmessage fragments have been received.

The broadcast module 206 is configured to broadcast the encoded messagefragments to one or more client devices 104. The broadcast module 206continually, periodically, or responsively broadcasts the messagefragments over the network 106. The broadcast module 206 may multicastthe message fragments over the network 106, allowing whichever clientdevices 104 are currently analyzing the network to receive the messagefragments. The broadcast module 206 may not require the client devices104 to confirm or otherwise acknowledge receipt of any messagefragments.

Still referring to FIG. 2, in some embodiments, each client device 104establishes an environment 210 during operation. The illustrativeenvironment 210 includes a firmware environment 212 and an operatingsystem 222. The various modules or components of the environment 210 maybe embodied as hardware, firmware, software, or a combination thereof.Additionally, in some embodiments, some or all of the modules of thefirmware environment 212 and/or the operating system 222 may beintegrated with, or form part of, other modules or software/firmwarestructures.

The firmware environment 212 includes a network module 214, a fountaindecoding module 216, an update management module 218, and a boot target220. The firmware environment 212 may be embodied as platform firmwarethat implements the uniform extensible firmware interface (UEFI)specification (i.e., a UEFI BIOS). Additionally or alternatively, thefirmware environment 212 may be embodied as firmware of themanageability engine 152. The network module 214 is configured toperiodically analyze the network 106 to receive any message fragmentsbroadcast by the management server 102. The network module 214 mayinclude, for example, a filter driver configured to filter multicastnetwork traffic received over the network 106.

The fountain decoding module 216 is configured to decode the messagefragments received by the network module 214. The fountain decodingmodule 216 may decode the completed message after receiving a sufficientnumber of message fragments. Due to the characteristics of fountain codealgorithms, the fountain decoding module 216 may not need to receive anyparticular message fragments or may not need to receive the messagefragments in any particular order. To decode message fragments receivedover several boot events, the fountain decoding module 216 may store themessage fragments (including decoded or partially decoded messagefragments) in the firmware cache 150. As described above, the completedmessage includes the management data supplied by the management server102.

The update management module 218 is configured to parse the completedmessage received from the management server 102, determine whether theincluded management data should be installed on the client device 104,and install the management data if necessary. The management data may beinstalled by updating platform configuration data 224 of the clientdevice 104. That platform configuration data 224 may be embodied as anyfiles, volumes, executables, firmware images, global variables, or othersettings affecting the operation of the client device 104. In someembodiments, the platform configuration data 224 may be embodied as oneor more software applications installed on the client device 104.

The boot target 220 is configured to terminate boot services andinitiate an operating system loader that in turn launches the operatingsystem 222. The boot target 220 may be selected among several potentialboot targets based on platform policy, for example according to theuniform extensible firmware interface (UEFI) specification. The boottarget 220 may cause the operating system 222 to launch after the clientdevice 104 receives one or more message fragments and determines thatthe message is not yet complete. Of course, the boot target 220 may alsocause the operating system 222 to launch in response to installingupdated management data.

Referring now to FIG. 3, in use, the management server 102 may execute amethod 300 for broadcasting management information. The method 300begins with block 302, in which the management server 102 receives orretrieves management data for installation on one or more client devices104. The management data may be received or retrieved from a networkadministrator, from a management application, from an enterprise server,or from any other entity or process responsible for management of theclient devices 104. The management data may be configured forinstallation on all of the client devices 104 or on a subset of theclient devices 104. The management data may be embodied as anyinformation, code, settings, or other data that may be used toprovision, configure, or otherwise manage the client devices 104. Forexample, in some embodiments, in block 304 the management server 102 mayreceive or retrieve a binary firmware image for installation on theclient devices 104. The binary firmware image may include one or moredrivers, applications, or configuration settings used by the clientdevice 104. For example, the binary firmware image may enable the use ofcertain enterprise-wide resources on each client device 104.Additionally or alternatively, in some embodiments in block 306 themanagement server 102 may receive or retrieve a certificate revocationlist. The certificate revocation list may be used by each client device104 for authenticating digital signatures. For example, as furtherdescribed below, the certificate revocation list may be a “dbx”certificate database specified by the UEFI specification and used duringa secure boot process.

In block 308, the management server 102 encodes the management data intoa number of message fragments using a fountain code algorithm. Afountain code—also known as a rateless erasure code—encodes a finite setof input symbols into an unbounded length of encoded output symbols. Inother words, the fountain code transforms a set of input data (such asthe management data) into an unbounded stream of encoded data.Typically, the original input symbols may be recovered from any set ofencoded symbols including more than a threshold number of encodedsymbols. An ideal fountain code would allow recovery of the inputsymbols given an equal number of encoded symbols; in practice, aslightly larger number of encoded symbols may be required to recover theinput symbols. Thus, the management server 102 applies a fountain codealgorithm to the management data or a formatted message including themanagement data (the input symbols) and generates encoded messagefragments (the encoded output symbols). The management server 102 mayemploy any suitable fountain code algorithm including but not limited toan LT code algorithm or a Raptor code algorithm.

In block 310, the management server 102 broadcasts the message fragmentsover the network 106, so that one or more client devices 104 may receivethe message fragments. The management server 102 may multicast themessage fragments or otherwise transmit each message fragmentsimultaneously to any receiving client devices 104. The managementserver 102 may broadcast the message fragments without waiting forreceipt of an acknowledgment or confirmation from any client device 104.The management server 102 may continually, periodically, or responsivelybroadcast the message fragments at any data rate appropriate for thenetwork 106.

In block 312, the management server 102 determines whether themanagement data has been or should be updated. For example, themanagement server 102 may receive a request from a network administratorto update the management information. If the management data should beupdated, the method 300 loops back to block 302 to receive the updatedmanagement data. If the management data should not be updated, themethod 300 loops back to block 310 to continue broadcasting the messagefragments over the network 106.

Referring now to FIG. 4, in use, a client device 104 may execute a bootprocess 400 according to the UEFI specification. The boot process 400may be executed whenever the client device 104 is powered on, includingwhen the client device 104 is powered on from a full electrical ormechanical “off” state, when the client device 104 is powered from a“soft-off” power state, when the client device 104 is reset or rebooted,or when the client device 104 is awoken from a sleep state. Duringexecution of the boot process 400, the client device 104 may be underfull control of the firmware environment 212. In block 402, the clientdevice 104 initializes platform hardware. For example, the client device104 may initialize particular components required to load or otherwiseprocess the firmware environment 212, for example the memory 144 and theI/O subsystem 142.

In block 404, the client device 104 loads and starts firmware images forone or more firmware drivers 406 or firmware applications 408. Firmwaredrivers 406 and firmware applications 408 are binary images that may bestored in a system partition of the data storage device 146. Theparticular drivers and applications to be loaded are platform-dependentand may be enumerated in global variables of the client device 104, forexample, in platform flash memory of the client device 104. The clientdevice 104 may enumerate the firmware drivers 406 and applications 408to be loaded and determine a required boot order. The boot order may bebased on dependencies between the firmware drivers 406 and applications408.

Firmware drivers 406 and applications 408 are similar, except thatapplications 408 are generally unloaded from the memory 144 afterreturning from their entry point, and drivers 406 generally stayresident in the memory 144 unless they return with an error code.Firmware drivers 406 and applications 408 may initialize or controlhardware of the client device 104. Firmware drivers 406 or applications408 may also install firmware protocol interfaces, which define functioncall interfaces and, after being installed, allow other firmware imagesto invoke provided services. For example, one or more firmware drivers406 or applications 408 may install protocols to allow the client device104 to access the communication circuit 148 and/or receive broadcastmanagement information. In some embodiments, a management update process410 may be performed as a firmware driver 406 and/or as a firmwareapplication 408. The management update process 410 may receive and/orinstall management data broadcasted by the management server 102, asfurther described below in connection with FIG. 5.

The boot process 400 further includes a secure boot subsystem 412. Thesecure boot subsystem 412 may authenticate every firmware image prior tothe image being loaded. The secure boot subsystem 412 may authenticatethe firmware image, for example, by validating a digital signatureassociated with the particular firmware image against a set of trustedcertificates. The secure boot subsystem 412 may maintain or otherwisereference one or more databases including authorized certificates (a“whitelist”) or forbidden certificates (a “blacklist” or a “certificaterevocation list”). For example, the UEFI specification defines thatallowed certificates are stored in the signature database “db” (alsoknown as the SECURITY_DATABASE) and that forbidden certificates arestored in the signature database “dbx” (also known as theSECURITY_DATABASE1). Authenticating each firmware image prior to loadingmay improve security by allowing the client device 104 to ensure thatall software executing during the boot process 400 (including each boottarget 416, described below) originates from a trusted source.

In block 414, the client device 104 determines and loads a boot target416. A boot target 416 is a firmware application that may be loaded andstarted by the client device 104. Therefore, the boot target 416 mayalso be subject to the secure boot subsystem 412. Boot targets aretypically operating system loaders, although the boot target may includediagnostic, maintenance, or management applications. The particular boottarget 416 selected may be specified in global variables of the clientdevice 104, for example stored in the platform flash memory. The globalvariables of the client device 104 may specify several boot targets 416,including a relative ordering of the boot targets 416. In someembodiments, the boot target 416 may be selected by a user of the clientdevice 104 through a menu or other means presented on the client device104. In some embodiments, the client device 104 may include a defaultboot target 416 or default rules for selecting a boot target 416.

In the boot target 416, the client device 104 hands off control to anoperating system loader 418. Such operating system loader 418 may not bestored in the system partition of the data storage device 146. As partof the handoff, the boot target 416 may advance to block 420 toterminate boot services, for example by calling the UEFI functionExitBootServices( ). Therefore, if such a boot target 416 is successful,the boot process 400 is complete, and the operating system 222 is infull control of the client device 104. Only firmware services that havebeen specifically designated as runtime-capable remain available aftercontrol has been passed to the operating system 222. Therefore, in manyembodiments, any firmware drivers 406 or applications 408 allowingaccess to the communication circuitry 148 are no longer available afterboot services are terminated. If boot services are not terminated by theboot target 416, for example if the operating system loader 418 fails toload the operating system 222, the client device 104 may attempt to loadanother boot target 416.

Referring now to FIG. 5, in use, a client device 104 may execute amethod 500 for receiving broadcast management data. The method 500begins with block 502, in which the client device 104 is booted up. Asdescribed above, the client device 104 may be booted in response topowering on the platform, resetting the platform, or waking the platformfrom a sleep state. As further described above, upon boot the clientdevice 104 may execute the boot process 400, including loading variousfirmware drivers 406 and applications 408. The various operations of themethod 500 may thus be performed by one or more firmware drivers 406 orfirmware applications 408.

In block 504, the client device 104 loads and initializes firmwaredrivers 406 and/or firmware applications 408. As described above, thefirmware drivers 406 and firmware applications 408 may be loaded as partof the boot process 400. The client device 104 may load firmware drivers406 and/or applications 408 to allow the client device 104 to receivebroadcast management data, for example network interface drivers. Inblock 506, the client device 104 loads a fountain code driver. Thefountain code driver may be configured to perform various operations ofthe method 500 including analyzing the network 106 and decoding receivedmessage fragments. The fountain code driver may be embodied as afirmware driver 406. Accordingly, the fountain code driver may be loadedafter dependencies are satisfied by loading other firmware drivers 406and/or firmware applications 408. After loading the fountain codedriver, the client device 104 may continue the boot process 400, forexample by loading additional firmware drivers 406 and/or firmwareapplications 408.

In block 508, the client device 104 analyzes the network 106 forincoming message fragments. The client device 104 may sample, read,open, or otherwise gather data from the network 106 to receive incomingmessage fragments. Those message fragments may have been generated bythe management server 102 using a fountain code algorithm, as describedabove. The client device 104 may sample for any network trafficappearing on the communication circuit 148; there is no need for theclient device 104 to wait for, acknowledge, or otherwise synchronizewith the management server 102. In some embodiments, in block 510 theclient device 104 may sample the network by filtering any multicast datareceived over the network 106 from the management server 102. Forexample, the client device 104 may install a filter driver to recognizeand process multicast data.

In block 512, the client device 104 determines whether a timeout foranalyzing the network 106 for message fragments has occurred. Asdescribed above, a fountain code requires a certain minimum number ofmessage fragments to decode the completed message. Therefore, analyzingthe network 106 for a longer time, and thereby potentially receivingmore message fragments, may reduce the amount of time and/or number ofplatform boot events required to decode the message. However, decreasingthe duration of the boot process is generally desirable for many clientdevices 104, and many operating systems 222 specify limits on totalduration of the boot process. Therefore, various embodiments may usedifferent timeouts in order to balance the amount of message fragmentssampled and the speed of the boot process. The length of the timeout maybe determined according to platform policy. For example, a consumerclient device 104 may use a relatively short timeout that may allowreceiving a single message fragment to emphasize speed in the bootprocess. As another example, an enterprise client device 104 may use arelatively long timeout on the order of a second or several seconds, toincrease the probability that many message fragments may be received foreach boot event. Additionally or alternatively, in some embodiments thetimeout may correspond to the end of the boot process 400. In otherwords, in those embodiments the client device 104 may analyze thenetwork 106 until the boot process 400 is completed and the operatingsystem 222 is ready to load. If the timeout has not expired, the method500 loops back to block 508 to continue analyzing the network 106. Ifthe timeout has expired, the method 500 advances to block 514.

In block 514, the client device 104 determines whether any messagefragments were received from the network 106 prior to expiration of thetimeout. If no message fragments were received, then the method 500branches ahead to block 536 to continue booting the client device 104.As described further below, the client device 104 may receive messagefragments in response to future boot events. If, however, any messagefragments were received prior to expiration of the timeout, the method500 advances to block 516.

In block 516, the client device 104 stores the received messagefragments in the firmware cache 150. As described above, the firmwarecache 150 may be embodied as any non-volatile storage medium accessibleto the firmware environment 212. Thus, the cached message fragments maybe used during subsequent boot events to decode the message. Of course,the firmware cache 150 may also include cached message fragments storedduring previous boot events. Accordingly, the message fragments mayaccumulate in the firmware cache 150 over several boot events.

In block 518, the client device 104 decodes the message fragments storedin the firmware cache 150 to generate at least a part of the sourcemessage. As described above, the client device 104 employs anappropriate decoding algorithm for the particular fountain code used toencode the message fragments. The particular operations and data storedby the client device 104 may depend on the fountain code in use. Forexample, for an LT code the client device 104 may iteratively updatevalues of message fragments stored in the firmware cache 150 based onthe contents of decoded fragments (i.e., fragments with a degree ofone). In some embodiments, individual message fragments may be partiallydecoded based on more-recently received message fragments. Continuingthe previous example, for an LT code the client device 104 may reducethe degree of a cached message fragment based on a more-recentlyreceived message fragment. The client device 104 may update the messagefragments in-place or otherwise store the decoded or partially-decodedmessage fragments in the firmware cache 150.

In block 520, the client device 104 determines whether a completemessage has been received. The method used to determine whether themessage is complete depends on the particular fountain code employed.For example, for an LT code the client device 104 may determine whetherall message fragments have a degree of one. If a complete message hasnot been received, the method 500 branches ahead to block 536 to run aboot target 416, as described below. If a complete message has beenreceived, the method 500 advances to block 522.

In block 522, the client device 104 parses the completed message toidentify the included management data. The message may be formatted inany data format suitable for transmission of the management data. Themessage may also include additional headers or other metadata describingthe management data. For example, the message may be formatted as afirmware volume containing the management data. Of course, in someembodiments the message may include the raw management data itself. Insome embodiments, in block 524 the client device 104 retrieves a binaryfirmware image from the message, such as a firmware driver 406 or afirmware application 408. In some embodiments, in block 526 the clientdevice 104 retrieves a certificate revocation list from the message,such as a “dbx” database as specified by the UEFI specification. Themanagement data may be embodied as the retrieved firmware image and/orcertificate revocation list.

In block 528, the client device 104 determines whether to install themanagement data. The client device 104 may apply any appropriatecriteria to determine whether to install the management data. Forexample the client device 104 may determine whether the management datais compatible with or applicable to the client device 104, or if themanagement data has already been installed on the client device 104. Ifthe client device 104 determines not to install the management data, themethod 500 branches ahead to block 536 to run a boot target 416, asdescribed below. If the management data is to be installed, the method500 advances to block 530.

In block 530, the client device 104 installs the management data byapplying the management data to the platform configuration data 224 ofthe client device 104. The client device 104 may perform any action,modify any setting, or store any files or data required to install themanagement data. Further, the management data may be installedtemporarily (e.g., into the memory 144) or permanently (e.g., into thedata storage 146). In some embodiments, in block 532 the client device104 may install the binary firmware image. For example, the clientdevice 104 may load and execute the firmware image and/or store thefirmware image into a system partition of the data storage 146. In someembodiments, in block 534 the client device 104 may install thecertificate revocation list. For example, the client device 104 maystore the “dbx” forbidden certificate database into a global variable inthe platform flash memory.

In block 536, the client device 104 runs a boot target 416, whichcompletes the method 500. As described above, the boot target 416typically starts an operating system loader 418 that in turn launchesthe operating system 222. After the operating system 222 is launched(and boot services are terminated), the firmware environment 212 is nolonger in control of the platform hardware of the client device 104.Thus, the client device 104 may not receive and/or respond to fountaincode message fragments during execution of the operating system 222. Themethod 500 may be executed again during the next platform boot event.For example, the method 500 may be executed again when the client device104 is physically power-cycled, rebooted, or wakes from a sleep state.

Although the preceding disclosure has described the method 500 as beingexecuted by the client device 104 in the firmware environment 212 inresponse to a platform boot event, it should be understood that in someembodiments the method 500 may be executed at any time the firmwareenvironment 212 is in control of the client device 104. Additionally oralternatively, in some embodiments parts or all of the method 500 may beexecuted by the manageability engine 152 in an out-of-band manner. Forexample, the method 500 may be executed by a combined security andmanageability engine (CSME) or other microcontroller included in asystem-on-a-chip (SoC) package of the client device 104. In suchexamples, the method 500 may be executed at runtime while the processor140 is otherwise active or during additional power state transitionsbeyond boot events, including transitions to or from active idle statesof the SoC (e.g., an SOix state). For example, the manageability engine152 may continually, periodically, or responsively analyze the network106 to receive message fragments broadcast by the management server 102and recover management data. The manageability engine 152 may apply themanagement data directly, for example by updating SECURITY_DATABASEand/or SECURITY_DATABASE1 directly if the manageability engine 152 hasdirect access to the UEFI variable store. Additionally or alternatively,the manageability engine 152 may expose the updates to those databasesfor update by the UEFI firmware upon a subsequent platform restartevent.

EXAMPLES

Illustrative examples of the technologies disclosed herein are providedbelow. An embodiment of the technologies may include any one or more,and any combination of, the examples described below.

Example 1 includes a client device for receiving broadcast managementinformation, the client device comprising a network module to analyze anetwork interface of the client device during a boot process of theclient device to receive message fragments broadcast by a managementserver; a fountain decoding module to (i) decode the message fragmentsto generate at least a part of a message using a fountain code decodingalgorithm, and (ii) determine whether the message is complete inresponse to generation of the at least a part of the message; and anupdate management module to (i) parse the message to identify managementdata included in the message by the management server in response to adetermination that the message is complete, and (ii) apply themanagement data to the client device.

Example 2 includes the subject matter of Example 1, and furtherincluding a firmware environment to establish the network module, thefountain code module, and the update management module.

Example 3 includes the subject matter of any of Examples 1 and 2, andwherein the fountain code decoding module is further to store themessage fragments in a firmware cache of the client device; to decodethe message fragments comprises to decode the message fragments storedin the firmware cache; and to determine whether the message is completecomprises to determine whether the message is complete in response todecoding of the message fragments stored in the firmware cache.

Example 4 includes the subject matter of any of Examples 1-3, andwherein the network module is to analyze the network interface and thefountain code decoding module is to decode the message fragments anddetermine whether the message is complete a second time in response to areboot of the client device.

Example 5 includes the subject matter of any of Examples 1-4, andfurther including a boot target to load an operating system of theclient device in response to a determination that the message is notcomplete or in response to application of the management data.

Example 6 includes the subject matter of any of Examples 1-5, andwherein the update management module is further to determine whether themanagement data is compatible with the client device in response toparsing of the message; and to apply the management data furthercomprises to apply the management data in response to a determinationthat the management data is compatible with the client device.

Example 7 includes the subject matter of any of Examples 1-6, andwherein the fountain code decoding algorithm comprises an LT code, aRaptor code, or a RaptorQ code.

Example 8 includes the subject matter of any of Examples 1-7, andwherein the management data comprises a binary firmware image includedin the message.

Example 9 includes the subject matter of any of Examples 1-8, andwherein the management data comprises a certificate revocation listincluded in the message.

Example 10 includes the subject matter of any of Examples 1-9, andwherein the certificate revocation list comprises a secure bootblacklist.

Example 11 includes the subject matter of any of Examples 1-10, andwherein the management data comprises a software application included inthe message.

Example 12 includes the subject matter of any of Examples 1-11, andfurther including a manageability engine comprising the network module,the fountain decoding module, and the update management module.

Example 13 includes the subject matter of any of Examples 1-12, andfurther including an in-band processor to execute an operating system ofthe client device; wherein the network module is further to analyze thenetwork interface of the client device during execution of the operatingsystem to receive message fragments broadcast by the management server.

Example 14 includes the subject matter of any of Examples 1-13, andwherein to analyze the network interface comprises to analyze thenetwork interface to receive message fragments encoded using a fountaincode encoding algorithm.

Example 15 includes the subject matter of any of Examples 1-14, andwherein to analyze the network interface comprises to filter multicastdata broadcast over a network by the management server.

Example 16 includes the subject matter of any of Examples 1-15, andwherein the network interface comprises a wireless network interface ofthe client device.

Example 17 includes a management server for broadcasting managementinformation, the management server comprising a fountain encoding moduleto encode management data into a plurality of message fragments using afountain code encoding algorithm; and a broadcast module to broadcastthe plurality of message fragments continually on a network accessibleby a plurality of client devices.

Example 18 includes the subject matter of Example 17, and wherein themanagement data comprises a binary firmware image.

Example 19 includes the subject matter of any of Examples 17 and 18, andwherein the management data comprises a certificate revocation list.

Example 20 includes the subject matter of any of Examples 17-19, andwherein the certificate revocation list comprises a secure bootblacklist.

Example 21 includes a method for receiving broadcast managementinformation, the method comprising analyzing, by a client device, anetwork interface of the client device during a boot process of theclient device to receive message fragments broadcast by a managementserver; decoding, by the client device, the message fragments togenerate at least a part of a message using a fountain code decodingalgorithm; determining, by the client device, whether the message iscomplete in response to decoding the message fragments; parsing, by theclient device, the message to identify management data included in themessage by the management server in response to determining that themessage is complete; and applying, by the client device, the managementdata to the client device.

Example 22 includes the subject matter of Example 21, and whereinanalyzing the network interface, decoding the message fragments,determining whether the message is complete, parsing the message, andapplying the management data are all performed by a firmware environmentof the client device.

Example 23 includes the subject matter of any of Examples 21 and 22, andfurther including storing, by the client device, the message fragmentsin a firmware cache of the client device, wherein: decoding the messagefragments comprises decoding the message fragments stored in thefirmware cache; and determining whether the message is completecomprises determining whether the message is complete in response todecoding the message fragments stored in the firmware cache.

Example 24 includes the subject matter of any of Examples 21-23, andfurther including rebooting the client device; and analyzing the networkinterface, decoding the message fragments, and determining whether themessage is complete a second time in response to rebooting the clientdevice.

Example 25 includes the subject matter of any of Examples 21-24, andfurther including loading, by the client device, an operating system ofthe client device in response to determining the message is not completeor in response to applying the management data.

Example 26 includes the subject matter of any of Examples 21-25, andfurther including determining, by the client device, whether themanagement data is compatible with the client device in response toparsing the message; wherein applying the management data furthercomprises applying the management data in response to determining thatthe management data is compatible with the client device.

Example 27 includes the subject matter of any of Examples 21-26, andwherein decoding the message fragments comprises decoding the messagefragments using one of an LT code, a Raptor code, or a RaptorQ code.

Example 28 includes the subject matter of any of Examples 21-27, andwherein applying the management data comprises installing a binaryfirmware image included in the message.

Example 29 includes the subject matter of any of Examples 21-28, andwherein applying the management data comprises installing to the clientdevice a certificate revocation list included in the message.

Example 30 includes the subject matter of any of Examples 21-29, andwherein installing the certificate revocation list comprises installingto the client device a secure boot blacklist.

Example 31 includes the subject matter of any of Examples 21-30, andwherein applying the management data comprises installing to the clientdevice a software application included in the message.

Example 32 includes the subject matter of any of Examples 21-31, andwherein analyzing the network interface, decoding the message fragments,and determining whether the message is complete are all performed by amanageability engine of the client device.

Example 33 includes the subject matter of any of Examples 21-32, andfurther including executing, by an in-band processor of the computingdevice, an operating system of the client device; and analyzing, by themanageability engine of the computing device, the network interface ofthe client device during execution of the operating system to receivemessage fragments broadcast by the management server.

Example 34 includes the subject matter of any of Examples 21-33, andwherein analyzing the network interface comprises analyzing the networkinterface to receive message fragments encoded using a fountain codeencoding algorithm.

Example 35 includes the subject matter of any of Examples 21-34, andwherein analyzing the network interface comprises filtering multicastdata broadcast over a network by the management server.

Example 36 includes the subject matter of any of Examples 21-35, andwherein analyzing the network interface comprises analyzing a wirelessnetwork interface of the client device.

Example 37 includes a method for broadcasting management information,the method comprising encoding, by a management server, management datainto a plurality of message fragments using a fountain code encodingalgorithm; and broadcasting, by the management server, the plurality ofmessage fragments continually on a network accessible by a plurality ofclient devices.

Example 38 includes the subject matter of Example 37, and whereinencoding the management data comprises encoding a binary firmware image.

Example 39 includes the subject matter of any of Examples 37 and 38, andwherein encoding the management data comprises encoding a certificaterevocation list.

Example 40 includes the subject matter of any of Examples 37-39, andwherein encoding the certificate revocation list comprises encoding asecure boot blacklist.

Example 41 includes a computing device comprising a processor; and amemory having stored therein a plurality of instructions that whenexecuted by the processor cause the computing device to perform themethod of any of Examples 21-40.

Example 42 includes one or more machine readable storage mediacomprising a plurality of instructions stored thereon that in responseto being executed result in a computing device performing the method ofany of Examples 21-40.

Example 43 includes a computing device comprising means for performingthe method of any of Examples 21-40.

Example 44 includes a client device for receiving broadcast managementinformation, the client device comprising means for analyzing a networkinterface of the client device during a boot process of the clientdevice to receive message fragments broadcast by a management server;means for decoding the message fragments to generate at least a part ofa message using a fountain code decoding algorithm; means fordetermining whether the message is complete in response to decoding themessage fragments; means for parsing the message to identify managementdata included in the message by the management server in response todetermining that the message is complete; and means for applying themanagement data to the client device.

Example 45 includes the subject matter of Example 44, and furtherincluding a firmware environment to establish the means for analyzingthe network interface, the means for decoding the message fragments, themeans for determining whether the message is complete, the means forparsing the message, and the means for applying the management data.

Example 46 includes the subject matter of any of Examples 44 and 45, andfurther including means for storing the message fragments in a firmwarecache of the client device, wherein: the means for decoding the messagefragments comprises means for decoding the message fragments stored inthe firmware cache; and the means for determining whether the message iscomplete comprises means for determining whether the message is completein response to decoding the message fragments stored in the firmwarecache.

Example 47 includes the subject matter of any of Examples 44-46, andfurther including means for rebooting the client device; and means foranalyzing the network interface, means for decoding the messagefragments, and means for determining whether the message is complete asecond time in response to rebooting the client device.

Example 48 includes the subject matter of any of Examples 44-47, andfurther including means for loading an operating system of the clientdevice in response to determining the message is not complete or inresponse to applying the management data.

Example 49 includes the subject matter of any of Examples 44-48, andfurther including means for determining whether the management data iscompatible with the client device in response to parsing the message;wherein the means for applying the management data further comprisesmeans for applying the management data in response to determining thatthe management data is compatible with the client device.

Example 50 includes the subject matter of any of Examples 44-49, andwherein the means for decoding the message fragments comprises means fordecoding the message fragments using one of an LT code, a Raptor code,or a RaptorQ code.

Example 51 includes the subject matter of any of Examples 44-50, andwherein the means for applying the management data comprises means forinstalling a binary firmware image included in the message.

Example 52 includes the subject matter of any of Examples 44-51, andwherein the means for applying the management data comprises means forinstalling to the client device a certificate revocation list includedin the message.

Example 53 includes the subject matter of any of Examples 44-52, andwherein the means for installing the certificate revocation listcomprises means for installing to the client device a secure bootblacklist.

Example 54 includes the subject matter of any of Examples 44-53, andwherein the means for applying the management data comprises means forinstalling to the client device a software application included in themessage.

Example 55 includes the subject matter of any of Examples 44-54, andfurther including a manageability engine comprising the means foranalyzing the network interface, the means for decoding the messagefragments, and the means for determining whether the message iscomplete.

Example 56 includes the subject matter of any of Examples 44-55, andfurther including means for executing, by an in-band processor of thecomputing device, an operating system of the client device; and meansfor analyzing, by the manageability engine of the computing device, thenetwork interface of the client device during execution of the operatingsystem to receive message fragments broadcast by the management server.

Example 57 includes the subject matter of any of Examples 44-56, andwherein the means for analyzing the network interface comprises meansfor analyzing the network interface to receive message fragments encodedusing a fountain code encoding algorithm.

Example 58 includes the subject matter of any of Examples 44-57, andwherein the means for analyzing the network interface comprises meansfor filtering multicast data broadcast over a network by the managementserver.

Example 59 includes the subject matter of any of Examples 44-58, andwherein the means for analyzing the network interface comprises meansfor analyzing a wireless network interface of the client device.

Example 60 includes a management server for broadcasting managementinformation, the management server comprising means for encodingmanagement data into a plurality of message fragments using a fountaincode encoding algorithm; and means for broadcasting the plurality ofmessage fragments continually on a network accessible by a plurality ofclient devices.

Example 61 includes the subject matter of Example 60, and wherein themeans for encoding the management data comprises means for encoding abinary firmware image.

Example 62 includes the subject matter of any of Examples 60 and 61, andwherein the means for encoding the management data comprises means forencoding a certificate revocation list.

Example 63 includes the subject matter of any of Examples 60-62, andwherein the means for encoding the certificate revocation list comprisesmeans for encoding a secure boot blacklist.

1. A client device for receiving broadcast management information, theclient device comprising: a network module to analyze a networkinterface of the client device during a boot process of the clientdevice to receive message fragments broadcast by a management server; afountain decoding module to (i) decode the message fragments to generateat least a part of a message using a fountain code decoding algorithm,and (ii) determine whether the message is complete in response togeneration of the at least a part of the message; and an updatemanagement module to (i) parse the message to identify management dataincluded in the message by the management server in response to adetermination that the message is complete, and (ii) apply themanagement data to the client device.
 2. The client device of claim 1,further comprising a firmware environment to establish the networkmodule, the fountain code module, and the update management module. 3.The client device of claim 1, wherein: the fountain code decoding moduleis further to store the message fragments in a firmware cache of theclient device; to decode the message fragments comprises to decode themessage fragments stored in the firmware cache; and to determine whetherthe message is complete comprises to determine whether the message iscomplete in response to decoding of the message fragments stored in thefirmware cache.
 4. The client device of claim 3, wherein the networkmodule is to analyze the network interface and the fountain codedecoding module is to decode the message fragments and determine whetherthe message is complete a second time in response to a reboot of theclient device.
 5. The client device of claim 1, wherein the managementdata comprises a binary firmware image included in the message.
 6. Theclient device of claim 1, wherein the management data comprises acertificate revocation list included in the message.
 7. The clientdevice of claim 6, wherein the certificate revocation list comprises asecure boot blacklist.
 8. The client device of claim 1, furthercomprising a manageability engine comprising the network module, thefountain decoding module, and the update management module.
 9. Theclient device of claim 8, further comprising an in-band processor toexecute an operating system of the client device; wherein the networkmodule is further to analyze the network interface of the client deviceduring execution of the operating system to receive message fragmentsbroadcast by the management server.
 10. A method for receiving broadcastmanagement information, the method comprising: analyzing, by a clientdevice, a network interface of the client device during a boot processof the client device to receive message fragments broadcast by amanagement server; decoding, by the client device, the message fragmentsto generate at least a part of a message using a fountain code decodingalgorithm; determining, by the client device, whether the message iscomplete in response to decoding the message fragments; parsing, by theclient device, the message to identify management data included in themessage by the management server in response to determining that themessage is complete; and applying, by the client device, the managementdata to the client device.
 11. The method of claim 10, wherein analyzingthe network interface, decoding the message fragments, determiningwhether the message is complete, parsing the message, and applying themanagement data are all performed by a firmware environment of theclient device.
 12. The method of claim 10, further comprising: storing,by the client device, the message fragments in a firmware cache of theclient device; rebooting the client device; and analyzing the networkinterface, decoding the message fragments, and determining whether themessage is complete a second time in response to rebooting the clientdevice, wherein: decoding the message fragments comprises decoding themessage fragments stored in the firmware cache; and determining whetherthe message is complete comprises determining whether the message iscomplete in response to decoding the message fragments stored in thefirmware cache.
 13. The method of claim 10, wherein applying themanagement data comprises installing a binary firmware image included inthe message.
 14. The method of claim 10, wherein applying the managementdata comprises installing to the client device a certificate revocationlist included in the message.
 15. The method of claim 14, whereininstalling the certificate revocation list comprises installing to theclient device a secure boot blacklist.
 16. One or more computer-readablestorage media comprising a plurality of instructions that in response tobeing executed cause a client device to: analyze a network interface ofthe client device during a boot process of the client device to receivemessage fragments broadcast by a management server; decode the messagefragments to generate at least a part of a message using a fountain codedecoding algorithm; determine whether the message is complete inresponse to decoding the message fragments; parse the message toidentify management data included in the message by the managementserver in response to determining that the message is complete; andapply the management data to the client device.
 17. The one or morecomputer-readable storage media of claim 16, further comprising aplurality of instructions that in response to being executed cause theclient device to: analyze the network interface, decode the messagefragments, determine whether the message is complete, parse the message,and apply the management data by a firmware environment of the clientdevice.
 18. The one or more computer-readable storage media of claim 16,further comprising a plurality of instructions that in response to beingexecuted cause the client device to store the message fragments in afirmware cache of the client device, wherein: to decode the messagefragments comprises to decode the message fragments stored in thefirmware cache; and to determine whether the message is completecomprises to determine whether the message is complete in response todecoding the message fragments stored in the firmware cache.
 19. The oneor more computer-readable storage media of claim 18, further comprisinga plurality of instructions that in response to being executed cause theclient device to: reboot the client device; and analyze the networkinterface, decode the message fragments, and determine whether themessage is complete a second time in response to rebooting the clientdevice.
 20. The one or more computer-readable storage media of claim 16,wherein to apply the management data comprises to install a binaryfirmware image included in the message.
 21. The one or morecomputer-readable storage media of claim 16, wherein to apply themanagement data comprises to install to the client device a certificaterevocation list included in the message.
 22. The one or morecomputer-readable storage media of claim 21, wherein to install thecertificate revocation list comprises to install to the client device asecure boot blacklist.
 23. A management server for broadcastingmanagement information, the management server comprising: a fountainencoding module to encode management data into a plurality of messagefragments using a fountain code encoding algorithm; and a broadcastmodule to broadcast the plurality of message fragments continually on anetwork accessible by a plurality of client devices.
 24. The managementserver of claim 23, wherein the management data comprises a binaryfirmware image.
 25. The management server of claim 23, wherein themanagement data comprises a certificate revocation list.